i386 ABI disagree with most other ABIs regarding alignment
of data type larger than 4 bytes: on most ABIs a padding must
be added at end of the structures, while it is not required on
i386.
So for most ABI struct mlx5_ib_create_srq get implicitly padded
to be aligned on a 8 bytes multiple, while for i386, such padding
is not added.
Tool pahole could be used to find such implicit padding:
$ pahole --anon_include \
--nested_anon_include \
--recursive \
--class_name mlx5_ib_create_srq \
drivers/infiniband/hw/mlx5/mlx5_ib.o
Then, structure layout can be compared between i386 and x86_64:
+++ obj-i386/drivers/infiniband/hw/mlx5/mlx5_ib.o.pahole.txt 2014-03-28
11:43:07.386413682 +0100
--- obj-x86_64/drivers/infiniband/hw/mlx5/mlx5_ib.o.pahole.txt 2014-03-27
13:06:17.788472721 +0100
@@ -69,7 +68,6 @@ struct mlx5_ib_create_srq {
__u64 db_addr; /* 8 8 */
__u32 flags; /* 16 4 */
- /* size: 20, cachelines: 1, members: 3 */
- /* last cacheline: 20 bytes */
+ /* size: 24, cachelines: 1, members: 3 */
+ /* padding: 4 */
+ /* last cacheline: 24 bytes */
};
ABI disagreement will make an x86_64 kernel try to read past
the buffer provided by an i386 binary.
When boundary check will be implemented, the x86_64 kernel will
refuse to read past the i386 userspace provided buffer and the
uverb will fail.
Anyway, if the structure lay in memory on a page boundary and
next page is not mapped, ib_copy_from_udata() will fail and the
uverb will fail.
This patch makes create_srq_user() takes care of the input
data size to handle the case where no padding was provided.
This way, x86_64 kernel will be able to handle struct mlx5_ib_create_srq
as sent by unpatched and patched i386 libmlx5.
Link: http://marc.info/[email protected]
Cc: [email protected]
Fixes: e126ba97dba9e ('mlx5: Add driver for Mellanox Connect-IB adapter')
Signed-off-by: Yann Droneaud <[email protected]>
---
drivers/infiniband/hw/mlx5/srq.c | 18 +++++++++++++++---
drivers/infiniband/hw/mlx5/user.h | 1 +
2 files changed, 16 insertions(+), 3 deletions(-)
diff --git a/drivers/infiniband/hw/mlx5/srq.c b/drivers/infiniband/hw/mlx5/srq.c
index 210b3eaf188a..38ca52181eb6 100644
--- a/drivers/infiniband/hw/mlx5/srq.c
+++ b/drivers/infiniband/hw/mlx5/srq.c
@@ -35,6 +35,7 @@
#include <linux/mlx5/srq.h>
#include <linux/slab.h>
#include <rdma/ib_umem.h>
+#include <rdma/ib_user_verbs.h>
#include "mlx5_ib.h"
#include "user.h"
@@ -84,10 +85,21 @@ static int create_srq_user(struct ib_pd *pd, struct
mlx5_ib_srq *srq,
int ncont;
u32 offset;
- if (ib_copy_from_udata(&ucmd, udata, sizeof(ucmd))) {
- mlx5_ib_dbg(dev, "failed copy udata\n");
- return -EFAULT;
+ if (udata->inlen - sizeof(struct ib_uverbs_cmd_hdr) < sizeof(ucmd)) {
+ if (ib_copy_from_udata(&ucmd, udata, sizeof(ucmd) -
sizeof(ucmd.reserved))) {
+ mlx5_ib_dbg(dev, "failed copy udata\n");
+ return -EFAULT;
+ }
+ } else {
+ if (ib_copy_from_udata(&ucmd, udata, sizeof(ucmd))) {
+ mlx5_ib_dbg(dev, "failed copy udata\n");
+ return -EFAULT;
+ }
+
+ if (ucmd.reserved != 0)
+ return -EINVAL;
}
+
srq->wq_sig = !!(ucmd.flags & MLX5_SRQ_FLAG_SIGNATURE);
srq->umem = ib_umem_get(pd->uobject->context, ucmd.buf_addr, buf_size,
diff --git a/drivers/infiniband/hw/mlx5/user.h
b/drivers/infiniband/hw/mlx5/user.h
index d44ecd2c2faf..d0ba264ac1ed 100644
--- a/drivers/infiniband/hw/mlx5/user.h
+++ b/drivers/infiniband/hw/mlx5/user.h
@@ -110,6 +110,7 @@ struct mlx5_ib_create_srq {
__u64 buf_addr;
__u64 db_addr;
__u32 flags;
+ __u32 reserved; /* explicit padding (optional on i386) */
};
struct mlx5_ib_create_srq_resp {
--
1.9.0
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